Study of sliding and rolling/sliding wear in complex micro-mechanical components is often accomplished experimentally using a pin-on-disc and twin-disc rolling/sliding tribometer respectively (conducted within the parameter space of the tribo-components). The present paper proposes an approach that involves a computationally efficient incremental implementation of Archard's wear model on the global scale (Global Incremental Wear Model-GIWM) for modeling sliding and slipping wear in such experiments. It will be shown that this fast simplistic numerical tool can be used to identify the wear coefficient from pin-on-disc experimental data and also predict the wear depths within a limited range of parameter variation. Further it will also be used to study the effect of introducing friction coefficient into the wear model and and also to model water lubricated experiments. A similar tool is presented to model wear due to a defined slip in a twin-disc rolling/sliding tribometer. The resulting wear depths from this tool is verified using two different finite element based numerical tools namely, the Wear-Processor, which is a FE post processor, and a userdefined subroutine UMESHMOTION in the commercial FE package ABAQUS. It will be shown that the latter two tools have the potential for use in predicting wear and the effective life span of any general tribosystem using the identified wear coefficient from relevant tribometry data.

Increasing requirements for higher power densities and further miniaturisation in microsystem technology result in highly loaded micromechanical systems. Regarding these applications, the friction and wear behaviour of selfmated Si 3 N 4 ceramic and WC-Co hardmetal has been characterized in laboratory micro tribometers. Experiments under unidirectional sliding and rolling conditions were carried out in air of 50% relative humidity as well as lubricated with water. Results from the model tests were used as input dataset for a numerical simulation tool Global Incremental Wear Model (GIWM) to predict volumetric wear as a function of operating conditions. The laboratory tests indicated that WC-Co as well as Si 3 N 4 are applicable for microsystems running in water, due to their high wear resistance and low friction coefficient. Furthermore it was shown, that the numerical simulation can help to reduce the experimental effort by reliable predicting wear under different operating conditions, provided that the active wear mechanisms are comparable.

Interfaces in bonded structures influence the mechanical behavior of components significantly, and often limit their load capacity. This requires nondestructive testing techniques allowing one to investigate the interaction forces in adhesive joints and to evaluate the quality of bonds. To this end the nonlinear stress-strain relationships of adhesives and adhesive interfaces, which cause a nonlinear modulation of ultrasonic waves in reflection as well as in transmission, may be exploited. Bonded interfaces which are much thinner than the ultrasonic wavelength can be approximately described only by the binding forces, without explicitly taking into account the material properties of the adhesive layers. These may be measured by the amplitudes and phases of ultrasonic waves transmitted through the interface. Measurements are presented on aluminum plates joined together by thin epoxy adhesive layers. A threshold behavior of the harmonics generated in the adhesive layer has been observed. Their amplitudes depend on the excitation following the power series expansion of a quasi-static interaction force curve, and their phases vary little for low-amplitude excitation. Exceeding the threshold causes a change in the response of the interface. The input and output ultrasonic amplitudes in the interface are calibrated interferometrically to obtain the absolute interaction force. The ultrasonic transmission data are related to destructive tensile tests of the adhesive bonds. IntroductionThe interfaces in bonded structures influence the mechanical behavior of components significantly. Therefore, an important task in nondestructive testing (NDT) is the investigation of the interaction forces in adhesive joints and the development of techniques to evaluate the bond quality. The load capacity of such joints is often limited by regions of weak bonding. As in all materials, the 403 Adhesion -Current Research and Application. Wulff Possart

Due to size effects the mechanical behavior of micro-components with dimensions in the range of some 100 lm and structure details of about 10 lm differs markedly from those of larger components. This is a crucial aspect for the design of micro-components for applications where demands for high strength are critical. The present study, which was performed in the frame of the Collaborative Research Centre 499 (SFB 499), approaches this issue by investigating the relationship between production process, microstructure and the mechanical properties of micro-specimens made from zirconia using two different feedstocks. The specimens were produced by a sintering process. The sintering temperature was varied between 1,300 and 1,500°C. Mechanical and tribological behavior of the specimens was determined by three-point bending tests as well as static and sliding friction tests, respectively. Properties derived from these tests were then correlated to the surface states in the specimens such as porosity, edge radius and roughness. The strength of the micro-specimens was found to be significantly influenced by these surface features. Whilst low porosity alone is not sufficient for high strength, notch effects resulting from pores as well as surface roughness can lower the strength. With increasing edge radius the strength of the material also increases. The porosity, edge radius and surface roughness were mathematically correlated with the strength to allow for a forecast. Within the SFB 499 feedstocks with specific properties were designed and reliable processes were developed to guarantee desirable surface roughness and porosity in the specimens. A characteristic bending strength of about 2,000 MPa is realizable in the micro-specimens within a good statistical reliability. The tribological tests revealed that the wear properties of the zirconia micro-components are strongly dependent on the quality of the feedstock.

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